1. Field of the Invention
The present invention relates to a system/method for detecting faults in the output signals from rotational speed sensors. In particular, the present invention relates to a system/method for detecting faults, particularly "tooth drop-out" type faults, in rotational speed sensors of the type comprising a relatively rotatable toothed rotor which rotates past a rotationally fixed sensor or stator member.
2. Description of the Prior Art
Rotational speed sensors which utilize a relatively rotatable toothed rotor which rotates past a relatively fixed sensor or the like are well known in the prior art. Examples of such speed sensor assemblies may be seen by reference to U.S. Pat. Nos. RE 30,522; 3,961,215; 4,862,025; 4,862,028 and 4,893,075, the disclosures of which are hereby incorporated herein by reference. Such rotational speed sensors are often used in connection with automated vehicular components/systems such as automatic fuel controls, automated transmission systems and/or vehicular anti-lock brake systems (ABS).
Typically, such rotational speed sensor assemblies are electromagnetic in nature and rely on the alignment of rotor teeth or spaces between rotor teeth rotating past a sensor to complete or break, respectively, a magnetic flux path to produce a digital or analog signal indicative of the rotational speed of the rotor.
While systems utilizing such rotational speed sensors are well known and widely used, they are not totally satisfactory as misalignments, jolts, damaged rotors or other causes may cause one or more tooth or pulse per measuring cycle not to be properly counted, i.e. "tooth drop-out". When this occurs, a false reading can be generated, usually indicating a much lower than actual speed and/or much greater than actual deceleration rate, which false reading if not detected can result in the automated system operating in an undesirable manner.